The present invention relates to a method for directing a certain amount of gas below the liquid surface in a solution reactor. More particularly, the invention relates to a method for directing a certain amount of gas to the bottom of a solution reactor, below the liquid surface.
The direction of the gas to the bottom of the reactor results in the dispersement of the gas into small bubbles, and the distribution of the gas as evenly as possible over the entire cross-sectional area of the reactor. When the gas discharges and disperses from the flexible-structured member in accordance with the invention, the reaction force due to the discharge puts the dispersion member into a whip-like movement which has a continuously decreasing radius of curvature. This movement cause a strong mechanical mixing in the liquid. This mixing is further enhanced by the strong gas jet discharging from the end of the dispersing member and changing place randomly. Due to this strong agitation, the solid in the reactor remains in motion and continuously maintains the produced good degree of suspension and does not accumulate into piles on the bottom of the reactor. Depending on the amount of gas, the rising gas bubbles produce effective vertical flows in the reactor which further mix the solid.
There are good and practical methods for mixing a pulverulent solid into a liquid to form a good suspension, or for dispersing a gas into a liquid. These methods have been described in the literature in, for example, Ullmanns "Encyclopadie der technischen Chemie", Band 2, pp. 260-281. the following references are to this work.
One example of apparatus for the mixing of a pulverulent solid into a liquid is a simple so-called pitch-blade mixer having a blade angle of 45.degree. (Ullmann, page 261, Abb 3, g) having a depressing effect. This produces a flow which is downward at the center of the reactor and upward along its sides, simultaneously producing turbulence important for reactions.
The following are standard methods for dispersing gas in a liquid. One device consists of a
nozzle or several nozzles from which the gas discharges, thereby forming small bubbles. Another device is PA1 a turbine mixer (Ullmann, page 261, Abb. 3, a) having vertical blades, in which gas directed under the mixer comes within the area of influence of the mixer and is dispersed into bubbles which are smaller, the greater the power used in the turbine. PA1 Gas is also dispersed via the use of so-called self-suction cross-pipes (Ullmann, Page 276, Abb. 19). That is the gas space branches out from the lower end of a hollow shaft, most commonly into four pipes, which are open at their tips. Due to the underpressure produced in the gas space by the rotating cross-pipe, the gas is discharged and dispersed into bubbles in the solution space in the reactor. It should be noted that when the temperature of the solution rises, the vapor pressure also rises, whereby the effect of the underpressure decreases.
However, the matter becomes more complicated when it is necessary to simultaneously disperse a gas effectively into small bubbles and, in addition, to maintain a pulverulent solid in good suspension in a liquid. None of the aforedescribed methods is capable of simultaneously satisfying both the requirements for dispersion and the maintenance of the suspension, sufficiently well, especially if the solid is coarse-grained and the density of the slurry is high.
In all cases, with the exception of nozzle methods, there are further difficulties when the solution level rises, since the mixing shaft has its own length limitations.
The object of the present invention is to direct gas into a solution reactor, preferably its lower part, to disperse it into small bubbles, and to distribute it as evenly as possible over the entire cross-sectional area of the reactor and to simultaneously form as good a suspension as possible of a pulverulent solid in a liquid and to maintain such suspension and to keep the solid in a strong turbulent motion.